Every time you start your car, drive around, park, and turn off your car, Dash counts that as a trip.
When you've finished a trip, you get a handy breakdown of your approximate starting and ending points, the total distance you drove, how long it took you, the amount of fuel you used measured in dollars (not in gallons or liters), and your average miles per gallon. You'll also see your Dash score.
For each trip, you get a Dash score, which is a rating of how many safe and efficient driving behaviors you practice, including sticking close to the speed limit, driving during safe weather conditions, and not using your phone while behind the wheel.
It's a scale from 1 to 100, and the higher the number, the better.
Dash can help you understand what's wrong with your car when the sometimes scary, often ambiguous check-engine light illuminates. If that happens, Dash sends you an alert with a description of what's wrong, an estimate of the cost of the repair, and information about nearby shops that might be able to help.
Dash has a social aspect to it, in which you can compare your scores and trips against you friends, but only if they are using the app. The idea is to see who's really the best driver among your friends.